Emotional-storyboarding is a participatory design method that informs emotional designs for children. When children draw emotional expressions for and craft stories about fictional characters, designers learn how children understand emotion and emotionally evocative experiences. This method overcomes two challenges in participatory design for children - access and verbal communication. We illustrate emotional-storyboarding by presenting a case study of designing a coloring book about overcoming negative emotions. In three hours, we engaged 66 children to create emotional stories using emotional- storyboarding. We also present four guidelines for using emotional-storyboarding to design with children: 1. Face-to-Face crowd-source at children's events 2. Make storyboarding simple, creative, and active 3. Engage children one-on-one to give them the confidence to express their stories and 4. Publicly praise children's stories. This case study suggests that emotional-storyboarding can inform meaningful emotional design for children while simultaneously providing children with an immediate positive emotional experience.